Vacuum lifter

ABSTRACT

A vacuum lifter apparatus for lifting sheet material articles comprises an upper chassis, a modular lower suction plate supported beneath the chassis, a controller and a source of vacuum air pressure, the suction plate comprising a suction lifting surface for providing vacuum lifting pressure to said articles. The modular suction plate has plural side-by-side modules, each module providing a different portion of the suction lifting surface and having one or more air outlets, outlets of one module separate from outlets of other modules and in fluid communication with the corresponding portion of the suction lifting surface and not with different portions of the suction lifting surface. The chassis comprises at least one air outlet connected to said source of vacuum air pressure, and a plurality of separate air flow channels through the chassis. Each air flow channel has an associated air flow valve and a valve actuator.

BACKGROUND a. Field of the Invention

The present invention relates to a vacuum lifter apparatus which may beused as part of a robotic sheet material lifting and handling system forlifting, moving and depositing sheet material articles, for examplesemi-rigid sheet plastic, sheet metal, paper-backed foam board, plywoodsheeting, solid cardboard, and corrugated cardboard and any other typesof sheet materials which in a production environment may need to be cutand handled by machinery.

b. Related Art

There is often a need in a manufacturing operation to individuallyhandle sheets of material, particularly those with sufficient strengthto support their own weight. A process step may be used to modify thematerial, or the material may simply be moved. The sheet material may,for example, be cut, creased, folded, embossed, printed upon,transported or stacked. The sheet material may need to be lifted andmoved from an input stack of sheets and placed on a cutting table, aprinting table or other type of processing work station, as part of theprocess. After cutting, cut material will be need to be moved off thetable and deposited at one or more stacks of cut or printed planiformarticles, which requires accurate stacking of one layer of sheetmaterial on another. In the following description, any such locationwhere planiform articles are to be placed on and/or lifted off by sheetmaterial handling equipment is referred to herein as a “work station”.

A specific example of a prior art work stations that may be used to cutor score fold lines in cardboard, are those supplied by Esko-Graphicsbvba (see https://www.esko.com/en/products/kongsberg-cutting-tables).Cuts in sheet material are made by a reciprocating vertical blade thatis moved on a 2-axis Cartesian robotic actuator that moves over the worksurface. Score lines can be formed in a similar manner by a scoringwheel mounted to the actuator. The cuts or fold lines for more than onesuch box may be made in a single sheet, depending on the size of theboxes being formed.

These work stations can be used with robotic sheet material handlersthat comprise a machine vision system and a vacuum lifting apparatus(also called a suction lifting apparatus) comprising a vacuum lifterapparatus that provides a downwardly oriented, planar suction liftingsurface, and an actuation system for lifting, horizontally moving andlowering the vacuum lifter apparatus. Any such actuation system will,for convenience, be referred to below as a “lifter actuation system”.Examples of downwardly oriented suction lifting surfaces include a flatmetallic plate, which is typically square or rectangular, perforatedwith an array of vacuum holes. The holes are connected to a source ofvacuum pressure for applying vacuum suction through an array of holes inthe plate. The source of vacuum pressure is usually at the higher end ofwhat is termed “low vacuum”, typically between about 0.1 and 0.5 ofatmospheric pressure.

The array of vacuum holes may be a square or rectangular array alongboth horizontal (X- and Y-) directions. The holes are on centres spacedapart by between about 5 mm and 30 mm, and more typically about 15 mm.The actuation system then moves the vacuum lifter apparatus in oppositehorizontal linear directions along both the X- and Y-directions, and inboth directions, up or down, along the vertical (Z-) direction. Theactuation system may be a robotic arm with multiple degrees of freedomof movement and rotation at a manipulating end of the arm. The vacuumplate may be supported centrally at a manipulating end of the arm. Suchan arm may lift and deposit sheet material within the reach of the armanywhere on the processing work station and adjacent stacking workstations, within the reach of the arm.

Other types of robotic sheet material handlers may alternatively beused, for example, a linearly movable gantry that spans the cutting andscoring work station, beneath which is supported the vacuum lifterapparatus. This is a simpler and more economical way for lifting, movingand depositing sheet material, but is limited to drawing from or forminga stack along the line of travel of the gantry. After placement on theprocessing work station, the sheet material may be held down in ahorizontal orientation by a vacuum hold-down, while cutting and scoringprocess, and/or an ink jet printing process is completed. Such cuttingoperations generate waste material that has to be separated later onfrom the desired, or processed, sheet material.

These production systems work well, but are limited in their speed ofmovement owing to the weight of the vacuum lifter apparatus and theactuating power of the actuation system. This problem has become moreacute as the speed of processing work stations has increased. From aneconomic perspective, it has also become ever more important to makegreater utilization of processing work stations as their capability andcost has increased.

Another common limitation is the need, when material is cut, is toseparate useful product and waste trimmings and to manually deal withdust or fragments on the processing work station after a cuttingoperation. The stacked material after processing on the processing workstation may also need sorting or separating into separate stacks.

An example of a situation where such problems arise is the cutting ofsheets of corrugated cardboard, prior to forming into box containers,for example by folding and gluing operations. The initial sheet stockmay have standard dimensions, such as, for example, 3.2 m×1.6 m. Priorto lifting and placing on the processing work station, the sheetmaterial may be in a relatively tall stack, for example between 1 m and2 m high. Quite often, the topmost layers of such stacks are not verylevel or flat, and may exhibit shallow dips and humps across the topface of the uppermost sheet. The vacuum lifter apparatus will haveeffectively a planar downwardly oriented lifting surface, which maytherefore not achieve a proper contact across a sufficient extent of thetop face to suck the top sheet into full contact with the liftingsurface, with the result that the top sheet is not lifted or securelyheld if lifted only by across a portion of its top face.

Generally, time is lost owing to the above difficulties during whichexpensive equipment is left idle, and even when such difficulties do notarise, workers may need to be on hand to monitor the performance of therobotic sheet material lifting and handling system.

It is an object of the present invention to provide a vacuum lifterapparatus which may, for example, be used as part of an automated sheetmaterial processing apparatus and also a method of using a vacuum lifterapparatus to lift sheet material articles, that addresses at least someof these problems.

SUMMARY OF THE INVENTION

According to the invention, there is provided a vacuum lifter apparatusfor lifting sheet material articles, comprising an upper chassis, amodular lower suction plate supported beneath the chassis, a controllerand a source of vacuum air pressure, the suction plate comprising asuction lifting surface for providing vacuum lifting pressure to saidarticles, wherein:

-   -   the modular suction plate has a plurality of side-by-side        modules, each module providing a different portion of the        suction lifting surface and having one or more air outlets, said        outlets of one module being separate from said outlets of other        modules and being in fluid communication with the corresponding        portion of the suction lifting surface and not with different        portions of the suction lifting surface;    -   the chassis comprises at least one air outlet connected to said        source of vacuum air pressure for conveying said vacuum pressure        to the suction lifting surface of the suction plate, and a        plurality of separate air flow channels through the chassis,        each of said channels leading from said outlets of one of said        modules to said outlet of the chassis; and    -   said apparatus further comprises for each air flow channel an        associated air flow valve and a valve actuator, the controller        being operatively connected said valves, and the controller        being configured, in use, to open and close said valves to        separately control the vacuum pressure transmitted along said        channels to each one of said modules whereby the vacuum pressure        conveyed to each one of said different portions of the suction        lifting surface is individually controllable by the controller.

The portions of the suction lifting surface may be arranged in an array.The controller may be configured to sequence opening of the valves toconvey the vacuum pressure to the suction lifting surface portions atdifferent times such that vacuum pressure appears at a first one ofthese portions first and a second one of these portions last, and thefirst and second portions being on opposite sides of the array ofsuction lifting surface portions.

There is preferably at least one intervening portion of the suctionlifting surface between the first and second portions. The controllermay then be configured to sequence the opening of the valves to conveythe vacuum pressure to the intervening portions sequentially in timesuch that such that the conveyed pressure appears as a wave spreadingacross the suction lifting surface starting at the first portion andending at the second portion.

The chassis may be separated at intervals from the suction plate upperside to provide a plurality of air chambers between the chassis andsuction plate, each air flow channel extending through one of thechambers.

Each suction module preferably comprises a housing, the housingcomprising opposite top and bottom walls. The bottom walls togetherprovide a lower side of the suction plate and the top walls each providethe outlets of the modules.

The bottom walls may each be perforated to provide orifices throughwhich, in use, air is drawn along air flow paths through the top walloutlets and into the channels towards the air outlet of the chassis toprovide the suction lifting pressure.

Also described herein is a vacuum lifter apparatus for lifting sheetmaterial articles, comprising an upper chassis joined to a substantiallyplanar lower suction plate and an airflow suction system for conveyingvacuum air pressure to the suction plate, wherein:

-   -   the suction plate comprises a lower side and an upper side, the        upper side of the suction plate being affixed to the chassis,        and the suction plate lower side providing a downwardly oriented        and substantially planar suction lifting surface for making        contact with the upper surface of said articles, said suction        lifting surface comprising a plurality of laterally adjacent        portions, each of said portions comprising a plurality of        orifices through which, in use, air is drawn along airflow paths        by the airflow suction system to provide a suction lifting        pressure; and    -   the airflow suction system comprises at least one air outlet for        connection to a source of vacuum air pressure, and between said        outlet and the suction plate at least one airflow manifold, said        manifold comprising a plurality of branched ends, said ends        being configured to convey said vacuum air pressure from said        outlet to corresponding portions of the suction plate.

Airflow paths from adjacent portions of the suction plate are preferablyisolated from each other by one or more air flow barriers between theadjacent portions.

The airflow paths for each portion of the suction plate preferably leadinto only one corresponding branched end of the manifold.

A lower side of the chassis may comprise a plurality ofdownwardly-concave recesses.

Preferably, these recesses are spanned by the upper side of the suctionplate along seams where the chassis is joined to the lower suctionplate, each of these recesses providing one of the branched ends of theairflow manifold. The seams are preferably air-tight.

Each recess may be bounded by a rim. The upper side of the suction platemay then be affixed to the chassis along each of the rims.

The suction plate is most preferably composed of a plurality of adjacentsuction modules. Each suction module may comprise a housing, the housingcomprising opposite top and bottom walls. The bottom walls may thentogether provide the lower side of the suction plate. Each top wallpreferably has at least one air outlet into a corresponding one of therecesses. The bottom walls may each be perforated with the orificesthrough which air is drawn.

The chassis may comprise a mounting portion for mounting the chassis toan actuator for lifting and/or moving the vacuum lifter apparatus duringuse. The suction plate is then supported beneath the chassis during use.

The mounting portion is preferably in a central portion of the chassis.

The mounting portion is preferably provided on an upper side of thechassis.

Also described herein is a vacuum plate lifting system for lifting sheetmaterial articles, comprising a vacuum lifter apparatus for liftingsheet material articles, a lifter actuation system configured to liftand/or move the vacuum lifter apparatus during use and a control system,the control system being configured to control the lifter actuationsystem during said movement, the vacuum lifter apparatus comprising:

-   -   a substantially horizontal suction plate comprising a perforated        suction lifting surface, said surface being downwardly oriented        for making contact with an upper surface of said articles to be        lifted;    -   an airflow suction system for conveying vacuum air pressure to        said perforated suction lifting surface;    -   at least one mount for connection of the suction plate to at        least one actuator of the lifter actuation system for lifting        and/or moving the suction plate during use, wherein:    -   the vacuum plate lifting system further comprises at least one        elongate bar movably mounted along an edge of the suction plate,        said bar comprising one or more nozzles, said nozzles being        connected to a source of air pressure for providing a suction        airflow of air into said nozzles;    -   a bar actuation system configured to drive movement of said bar        between a raised orientation in which the bar is raised relative        to a level of said suction lifting surface and a lowered        orientation in which the bar is substantially at or below the        level of said suction lifting surface whereby, in use, said        suction airflow acts on a surface to be cleaned beneath said        suction lifting surface when said bar is in the lowered        orientation; and    -   wherein the control system is operable to control the operation        of the lifter actuation system and the operation of the bar        actuation system to provide a sweeping movement of said bar in        said lowered orientation across said surface to be cleaned        whereby said suction airflow sweeps across said surface to be        cleaned.

The suction plate may be substantially square or rectangular in ahorizontal plane. The bar may then be mounted along a substantiallystraight edge of the suction plate.

In a preferred embodiment, there is one bar mounted along an edge of thesuction plate.

The bar may be movably mounted to the suction plate at a pair of hingesproximate opposite ends of the bar.

Each of the hinges is preferably pivotably mounted to an edge of thesuction plate adjacent the edge of the suction plate along which the baris mounted.

The, or each, nozzle may be an elongate slot in an outer face of thebar, the slot then extending in a direction substantially parallel withthe length of the bar.

The lifter actuation system preferably comprises a robotic armconfigured to lift and/or move the vacuum lifter apparatus during use.The invention in its various aspects is, however applicable to othertypes of movement actuator for lifting and moving the vacuum lifterapparatus.

The vacuum lifter apparatus may comprise at least one mount on an uppersurface thereof, the actuation system being physically connected to thesuction plate via this mount.

In particular, the suction plate is preferably supported beneath themount in a substantially horizontal orientation for lifting anddepositing the sheet material articles

The bar actuation system may comprise a pneumatic lifter acting betweenan upper surface of the suction plate and the bar.

Also described herein is a method of using a vacuum plate lifting systemto sweep dust or debris from a surface to be cleaned, the vacuum platelifting system being as claimed in any preceding claim, and the methodcomprising the steps of:

-   -   using the control system to control the movement of said bar by        the bar lifter system to place said bar in the raised        orientation;    -   with said bar in the raised orientation, using the control        system to control the movement of the vacuum lifter apparatus by        the lifter actuation system during lifting by the suction        lifting surface of a sheet material article from a work surface        and subsequent deposition of said lifted article away from the        work surface;    -   using the control system to control the movement of said bar by        the bar lifter system to place said bar in the lowered        orientation;    -   after said deposition, using the control system to control the        movement of the vacuum lifter apparatus by the lifter actuation        system to return the suction lifting surface above a surface to        be cleaned; and    -   with said bar in the lowered orientation, applying said suction        airflow across said surface to be cleaned while using the        control system to control a sweeping movement of said bar across        said surface to be cleaned whereby said vacuum airflow sweeps        across said surface to be cleaned to remove dust or debris from        said surface.

The surface to be cleaned may be the work surface, in which case thevacuum sweep may be performed prior to subsequent deposition of anothersheet material article on the work surface.

The surface to be cleaned may, however, be another surface, for examplea top surface of the deposited sheet, or the top surface of the nextsheet to be lifted.

Also described herein is a vacuum plate lifting system for lifting sheetmaterial articles, comprising a vacuum lifter apparatus for liftingsheet material articles, a lifter actuation system configured to liftand/or move the vacuum lifter apparatus during use and a control system,the control system being configured to control the lifter actuationsystem during said movement, the vacuum lifter apparatus comprising:

-   -   a substantially horizontal suction plate comprising a perforated        suction lifting surface, said surface being downwardly oriented        for making contact with an upper surface of said articles to be        lifted;    -   an airflow suction system for conveying vacuum air pressure to        said perforated suction lifting surface;    -   at least one mount for connection of the suction plate to at        least one actuator of the lifter actuation system for lifting        and/or moving the suction plate during use, wherein:    -   at least one suction lifter proximate an edge of the suction        plate, said suction lifter comprising a downwardly oriented        suction cup, said cup being movably mounted in a substantially        vertical direction relative to the suction plate and being        connected to a source of air pressure for providing air suction        to said cup for plucking upwards a local area of said of        articles to be lifted;    -   a suction cup actuation system configured to drive said movement        of the suction cup between a raised orientation in which the        suction cup is raised relative to a level of said suction        lifting surface and a lowered orientation in which the suction        cup is substantially at or below the level of said suction        lifting surface whereby, in use, said air suction is directed        substantially downwardly towards a sheet material article to be        lifted when said suction cup is in the lowered orientation;    -   wherein the control system is operable to control the operation        of the lifter actuation system and the operation of the suction        cup actuation system to initially pluck said local area of said        article to be lifted prior to applying said vacuum air pressure        to said perforated suction lifting surface to lift the remainder        of said article.

The suction plate may have a substantially square or rectangular profilein a horizontal plane. In a preferred embodiment, there are three of thesuction lifters with two of these lifters being mounted along adjacentedges of the suction plate proximate a corner of the rectangular orsquare profile. A third one of these lifters may then be mountedproximate a vertex of this profile between the adjacent edges.

In a preferred embodiment, the suction plate is composed of a pluralityof adjacent suction modules, each module providing a portion of theperforated suction lifting surface. The airflow suction system may beconfigured to convey vacuum air pressure to each of these portions viacorresponding control valves, the control system being configured tocontrol the operation of the valves to individually control the vacuumair pressure provided to each of the suction lifting surface portions.

The portions of the perforated suction lifting surface may include aproximal set of portions relatively closer to one of the suction liftersand a distal set relatively further away from this suction lifter. Thecontrol system may then be configured to sequence the operation of thevalves to provide the vacuum air pressure to this proximal portion priorto this distal portion following the initial plucking of the local area.

Also described herein is a method of using a vacuum plate lifting systemfor lifting sheet material articles, the vacuum plate lifting systemcomprising:

-   -   at least one suction lifter proximate an edge of the suction        plate, said suction lifter comprising a downwardly oriented        suction cup, said cup being movably mounted in a substantially        vertical direction relative to the suction plate and being        connected to a source of air pressure for providing air suction        to said cup for plucking upwards a local area of said of        articles to be lifted;    -   a suction cup actuation system configured to drive said movement        of the suction cup between a raised orientation in which the        suction cup is raised relative to a level of said suction        lifting surface and a lowered orientation in which the suction        cup is substantially at or below the level of said suction        lifting surface whereby, in use, said air suction is directed        substantially downwardly towards a sheet material article to be        lifted when said suction cup is in the lowered orientation;    -   wherein the method comprises the steps of:    -   using a control system to control the movement of said suction        cup by the suction cup lifting system to place said suction cup        in the lowered orientation;    -   using the control system to control the movement of a vacuum        lifter apparatus by a lifter actuation system to position the        suction lifting surface over a sheet material article to be        lifted;    -   with the suction cup in the lowered orientation and the suction        lifting surface over said sheet material article to be lifted,        applying said air suction to said cup to pluck upwards a local        area of said of said article to be lifted;    -   with said local area being lifted, using an airflow suction        system to convey vacuum air pressure to a perforated suction        lifting surface to lift the remainder of said article to said        suction lifting surface.

The method may further comprise the step of using the control system tocontrol the movement of the suction cup by the suction cup liftingsystem to place the suction cup in the raised orientation once theairflow suction system is being used or is about to be used to conveyvacuum air pressure to the perforated suction lifting surface to liftthe remainder of the article.

The method may further comprise using the control system to control theoperation of valves to individually control the vacuum air pressureprovided to each of several portions of the perforated suction liftingsurface during lifting of the remainder of said article to said suctionlifting surface.

The control system may be configured to sequence the operation of thevalves to provide vacuum air pressure to a portion of the suctionlifting surface relatively closer to said suction cup prior to providingvacuum air pressure to another portion of the suction lifting surfacerelatively farther away from the suction cup.

Also described herein is a vacuum lifter apparatus for lifting sheetmaterial articles, comprising an upper chassis joined to a substantiallyplanar lower suction plate and an airflow suction system for conveyingvacuum air pressure to the suction plate, wherein:

-   -   the suction plate comprises a plurality of suction plate        modules, each of said modules comprising a housing with a        substantially hollow interior and each of said housings being        located laterally adjacent at least one other of said housings;    -   each of said housings comprises a lower plate, an upper plate        and at least one side plate, each housing being affixed to said        laterally adjacent housing along a seam between adjoining pairs        of side plates;    -   said upper plates each comprise at least one opening and said        lower plates are each perforated with a plurality of orifices        through which, in use, air is drawn along airflow paths through        said interior and out of said opening by the airflow suction        system to provide, in use, on a lower side of the suction plate        a substantially planar suction lifting surface for applying a        suction lifting pressure to an upper surface of said sheet        material articles to be lifted;    -   said upper plates together provide an upper side of the suction        plate, the upper side of the suction plate being affixed to the        chassis at each one of said housings.

Each suction plate module is therefore directly supported by thechassis.

The upper and lower plates are preferably secured spaced apart and fixedtogether within the housing interior by a reinforcing structure thatextends between the lower and upper plates.

The reinforcing structure may be sandwiched between a lower tray and anupper lid. In a preferred embodiment, the tray and lid may each be of ametallic material. Other suitable materials may alternatively be used,for example moulded plastic materials or composite fibre-reinforcedmaterials.

The tray may provide the lower plate and the lid may provide the upperplate.

Preferably, the side plates each comprise adjoining first and secondmembers, the first member extending upwards from an edge of thecorresponding lower plate along a fold in the material of the tray andthe second member extending downwards from an edge of the correspondingupper plate along a fold in the material of the lid.

The reinforcing structure is preferably sandwiched between the lowertray and the upper lid.

The lower plate will, in general, have a periphery. The tray maycomprise around this periphery an up-turned lip.

The upper plate will, in general, have a periphery. The lid may comprisearound this periphery a down-turned lip.

In a preferred embodiment, the lip of the lid inter-engages with the lipof the tray, these lips being bonded together, for example by anadhesive, around said peripheries of the lower and upper plates.

The reinforcing structure is preferably an open-cell structure extendingbetween the lower and upper plates and providing a plurality of channelsfor air drawn through said orifices to flow to the, or each, opening inthe upper plate.

The open-cell structure is most preferably a honeycomb structurecomprising a plurality of honeycomb cells. The cells are bounded bywalls that extend between the upper and lower plates to provide verticalair flow paths, where these intersect with openings in one or bothplates, and walls between adjacent cells having at least one holetherethrough to provide lateral air flow paths.

The upper and lower ends of the cell walls are most preferably bonded,for example by means of an adhesive, to, respectively, the upper andlower plates.

The airflow suction system preferably comprises a plurality of airflowchannels, each airflow channel extending through the chassis from an airinlet to an air outlet. The air outlets are preferably connected to asource of vacuum pressure and the air inlets are preferably configuredto receive the air drawn along airflow paths.

Preferably, different ones of the air inlets are configured to receiveair from different ones or different groupings of the suction platemodules.

The suction lifting surface may comprise a plurality of individuallycontrollable sections, each section comprising at least one of thesuction plate modules.

The airflow suction system may comprise a control system and a pluralityof airflow control valves, each of these valves being associated withone of the sections of the suction lifting surface and the controlsystem may be configured to control the operation of the valves so thatthe airflow to said sections is individually controllable by the controlsystem.

In a preferred embodiment, the upper, lower and side plates may each beof a metallic material. Other suitable materials may alternatively beused, for example moulded plastic materials or compositefibre-reinforced materials. At least one of the adjoining pairs of sideplates may comprise a member that extends upwards from an edge of thecorresponding lower plate along a fold in the material to provide anupwardly folded side plate member.

The folded side plate member may extend upwards beyond a plane definedefined by the corresponding upper plate to present a tab. In apreferred embodiment, a pair of opposed tabs are bonded together to forma flange. This tab or flange may then be affixed to the chassis,preferably the lower side of the chassis.

The lower side of each suction plate module is therefore directlysupported by the chassis by the tabs.

The lower side of the chassis may have at least one downwardly facingslot. The, or each tab may then be affixed to the chassis within theslot.

Preferably, at least one pair of adjacent housings comprise a pair ofadjoining tabs, said adjoining tabs both being affixed to the chassiswithin a common one of said slots.

In this way, the weight of the corresponding housing including theweight of a lifted article is at least partially transmitted to thechassis via the tabs.

Also described herein is a vacuum lifter apparatus for lifting sheetmaterial articles, comprising an upper chassis and a lower suctionplate, the upper chassis having at least one air outlet for conveyingvacuum pressure to the suction plate along a plurality of air flow pathsthrough the chassis and suction plate to provide suction liftingpressure to an upper surface of said articles to be lifted, wherein:

-   -   the suction plate comprises a lower side and an upper side, the        suction plate having a substantially hollow interior between        said lower and upper sides, the upper side of the suction plate        being affixed to the chassis, and the suction plate lower side        providing a downwardly oriented planar suction lifting surface        for making contact with the upper surface of said articles, and        said suction lifting surface comprises a plurality of laterally        adjacent portions, each of said portions comprising a plurality        of orifices through which, in use, air is drawn along said        airflow paths to provide a suction lifting pressure; and    -   the chassis is separated at intervals from the suction plate        upper side to provide a plurality of air chambers between the        chassis and suction plate, each air chamber being configured to        convey said vacuum pressure to a corresponding one of said        portions; and    -   each of said portions of the suction plate has a laterally        extending portion that extends laterally away from a        corresponding one of said air chambers, and the substantially        hollow interior of the suction plate providing lateral airflow        whereby suction lifting pressure is provided to said laterally        extending portions from each corresponding air chamber.

The suction plate is most preferably composed of a plurality of adjacentsuction modules. Each suction module may comprise a housing, the housingcomprising opposite top and bottom walls. The bottom walls togetherprovide the lower side of the suction plate and the top walls each haveat least one air outlet leading into a corresponding one of the airchambers. The bottom walls are each perforated to provide the orificesand through which, in use, air is drawn along the air flow paths throughthe top wall outlets and into the chambers towards the, or each airoutlet of the chassis, to provide the suction lifting pressure.

For each of the suction lifting surface portions there is, in apreferred embodiment, just one suction module. The, or each, air outletof each top wall may then lead into a corresponding one of the airchambers.

At least one air flow control valve may be provided along at least oneof the air flow paths in order to control the suction lifting pressureto the suction modules.

Preferably, for each chamber, an air-tight seal is provided between theupper side of the suction plate and the chassis. This air-tight seal ismost preferably provided around each chamber where the upper side of thesuction plate is affixed to the chassis.

Each of said housings may comprise a substantially hollow interiorbounded by opposite top and bottom walls.

Each of the housings may comprise a lower plate, an upper plate and atleast one side plate, and each one of the housings may be affixed to alaterally adjacent another one of said housings along a seam betweenadjoining pairs of side plates.

The vacuum lifter apparatus may further comprise an airflow suctionsystem for conveying vacuum air pressure to the suction plate, theairflow suction system comprising a source of vacuum air pressure towhich the air outlet is connected.

There may be, associated with each one of the air chambers, an airflowcontrol valve for controlling the volume of air drawn along the airflowpaths.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be further described, by way of example only, andwith reference to the accompanying drawings, in which:

FIG. 1 is a perspective view of a sheet material cutting work stationand a vacuum plate lifting system according to a preferred embodiment ofthe invention, the lifting system comprising a vacuum lifter apparatusfor lifting and depositing sheet material articles, a sheet materiallifter actuation system configured to raise, lower and move the vacuumlifter apparatus and a control system configured to control theoperation of the vacuum lifter apparatus and actuation system duringuse;

FIG. 2 is a perspective view of the vacuum lifter apparatus of FIG. 1,showing how this is comprised of an upper chassis joined to asubstantially planar lower suction plate composed of a plurality ofadjacent suction modules;

FIG. 3 is an exploded view of the vacuum lifter apparatus of FIG. 2,showing the how the suction plate comprises eight suction modules andhow the chassis has an elongate central spine from which eight lobesextend transversely, each lobe overlapping just one of the modules;

FIG. 4 is a perspective view of the underside of the chassis of FIG. 3,showing how each chassis lobe has a hollow, generally arched interiorproviding a corresponding recess, each recess being partitioned fromadjacent recesses by a dividing wall that extends the length of thecentral spine and by three transverse branches between longitudinallyadjacent pairs of lobes so that each recess provides a correspondingchamber when the chassis is affixed to the suction plate, each chamberhaving a valve aperture in an upper wall of a main chassis housing;

FIG. 5 is an exploded view from underneath of the chassis of FIG. 3,showing the main chassis housing, the components used to form thedividing wall and eight corner brackets used to reinforce base cornersof each of the lobes;

FIG. 6 is a view of the underside of the main chassis housing of FIG. 5and components affixed to an upper side of the main chassis housingupper wall, including eight valve mechanisms and a central mountingportion of the chassis by which the vacuum lifter apparatus is attachedto the end of a robot arm of the lifter actuation system;

FIG. 7 is an enlarged view from above of one end of the vacuum lifterapparatus of FIG. 2, with a protective cover having been removed toexpose one set of four of the valve mechanisms, each of the valvemechanisms being mounted on a common mounting plate that comprises on alower side four valve plate seats each of which has an upper valveaperture and a slideable valve plate driven by a pneumatic pistonactuator mounted on an upper side of the mounting plate;

FIG. 8 shows an enlarged view of the set of four valve mechanisms ofFIG. 7;

FIG. 9 shows an underside of the common mounting plate of FIG. 7,without the four slideable valve plates and associated actuators;

FIG. 10 shows an enlarged view of part of the underside of the commonmounting plate of FIG. 7, with the one of the slideable valve platesmoved to fully close the associated valve aperture;

FIG. 11 shows a gasket which provides a seal between the underside ofthe common mounting plate around each one of the four valve seats, andan upper side of the main chassis housing upper wall;

FIG. 12 is a view of the eight suction modules when joined togetheralong vertically parallel seams which include upwardly extending tabsthat insert into corresponding slots in the centre lines of the dividingwall, and showing how each module in an upper side has five air outletsthrough which air is drawn into a corresponding one of the recesses inthe underside of the chassis;

FIG. 13 is an enlarged view showing four adjacent modules of FIG. 12prior to abutment and affixing along the vertically parallel seams;

FIG. 14 is an enlarged view of the four adjacent modules of FIG. 13after affixing;

FIG. 15 is an exploded view of one of the suction modules, showing howthis has a hollow housing comprising opposite top and bottom wallsspanned across their full extent by a reinforcing honeycomb structure,only part of which is shown in FIG. 15 for clarity;

FIG. 16 is an enlarged view of the honeycomb structure of FIG. 15,showing how each of six hexagonal side walls is perforated to allowcross-flow of air within the reinforcing structure;

FIG. 17 is an enlarged perspective view of part of a second embodimentof vacuum plate module, showing the arrangement of holes in the lowerwall of the vacuum plate with respect to an internal reinforcingstructure formed from a grid of interlaced linear walls;

FIG. 18 is an enlarged perspective view of the interlaced linear wallsof FIG. 17, with one wall removed to show how these slot together;

FIG. 19 is an enlarged perspective view of one corner of the vacuumlifter apparatus of FIG. 1 showing two suction lifters proximate an edgeof the suction plate, each suction lifter extending through one of thesuction modules to present a suction cup for lifting an edge of a sheetmaterial article;

FIG. 20 is a schematic cross-section through the assembled modulehousing and reinforcing honeycomb matrix, taken along line XX-XX of FIG.19, showing how the holes have internally raised rims which preventadhesive within the module housing from blocking the hole;

FIG. 21 is a perspective view of one of the suction lifters of FIG. 19;

FIG. 22 is a cross-section view through the suction lifter of FIG. 21;

FIG. 23 is an enlarged perspective view of one corner of the suctionplate of FIG. 1, showing mounting rails extending along the sides of thesuction plate;

FIG. 24 is a perspective view in isolation of one of the mounting railsof FIG. 23;

FIG. 25 is an enlarged perspective view from below of one corner of thevacuum lifter apparatus of FIG. 1, showing an elongate bar movablymounted along an edge of the suction plate, the bar being in a raisedorientation and having nozzles for downwardly directing a vacuum suctionalong the length of the bar; and

FIG. 26 is an enlarged perspective view of the corner and bar of FIG.25, showing the bar in a lowered orientation and being used to applysuction air flow onto the empty work surface of the cutting work stationas the vacuum lifter apparatus is moved by the lifter actuation systemso that the vacuum sweeps across the work surface.

DETAILED DESCRIPTION

FIG. 1 shows a sheet material processing apparatus 1, comprising a sheetmaterial cutting work station 2 and a vacuum plate lifting system 3. Thevacuum plate lifting system comprises a vacuum lifter apparatus 4 forlifting and depositing sheet material articles 5, in this examplerectangular cardboard sheets, and a sheet material lifter actuationsystem 6, which in this example includes a five-axis robotic arm 7configured to raise, lower and move the vacuum lifter apparatus 4 whilstkeeping it level. The lifter actuation system 6 also comprises a controlsystem 8 configured to control the operation of the vacuum lifterapparatus and lifter actuation system.

The mechanical details of the robotic arm 7, and the general way inwhich it may be controlled by the controller 8 to move above five axes,are not central to the invention, and will also be familiar to thoseskilled in the art, and so will not be further described in detail.

In this example, the sheets are moved between three locations by thelifting system 3. Blank sheets or “blanks” 5 are initially stacked toone side of the work station 2. The lifter actuation system 4, shown inmore detail in FIG. 2, has a substantially planar suction plate 10 whichis maintained in a substantially horizontal or level orientation whilebeing moved forwards or backwards along orthogonal horizontal X- andY-axes and upwards or downwards along a vertical Z-axis. As shown inFIGS. 15, 17, 23 and 25, the suction plate 10 has on a lower side 29 asubstantially planar downwardly orientated suction lifting surface 11provided by a lower wall 12 perforated by an array of holes or orifices13. As will be explained in detail below, the holes are connected to anairflow suction system for conveying vacuum air pressure to theperforated suction lifting surface including a source of negative, orvacuum, air pressure 14 for attracting, making contact with and holdingan upper surface 9 of a sheet material article to the suction liftingsurface. The operation of the lifter actuation system 4, the robotic arm7 and source of vacuum pressure 14 is controlled by the controller 8.

In this example, the work station 2 is an automated cutting table, suchas that supplied by supplied by Esko-Graphics bvba under the brand name“Kongsberg Automate” (Trade Mark). The automated cutting table 2 has afixed cutting surface 15 provided by a rectangular table top or plate 16perforated by an array of holes 17 connected to a controllable source ofvacuum pressure (not shown) to provide a vacuum hold-down. In this way,the table can securely hold down and release any sheet material placedon the table surface 15. The principles of the invention do not,however, require use of any particular type of work station or the useof a vacuum hold down on the surface where sheet material articles aredeposited which could, for example, simply be a stack of similararticles.

In this example, however, sheet material articles are lifted by thesuction plate of the vacuum lifter apparatus one at a time from an inputstack 18 of fresh uncut sheets 5 onto the cutting surface 15, and thenafter cutting along cut lines 19 and scoring along fold lines 19′(indicated schematically by dashes) by a movable blade 20 and scoringwheel (not shown), are lifted, moved and deposited by the apparatusplate onto an output stack 18′ of processed sheets 5′. The blade 20 is areciprocating vertical blade driven by a cutting head 20′ that ismovably mounted on a rail such that the blade can be moved in X- andY-directions. Other types of cutters may, however, be used, dependingmainly on the material to be cut. The blade will normally be surroundedby a cylindrical shield - this is omitted from the drawings so that theblade can be seen. The score lines, or crease lines 19′, may optionallybe formed in a similar manner by a scoring wheel mounted to theactuator, to facilitate folding of the cardboard material.

In this example, the processed sheets have a central portion providinguseful material 21 for a folded cardboard box and a peripheral portionwhich is waste material 21′.

In FIG. 1, cutting and creasing operations have just been completed forone cardboard sheet 5′ on the table cutting surface 15. The robotic arm7 is shown in the process of moving into position to lift this processedsheet off the table surface and onto the output stack 18′.

The suction plate 10 is rectangular, with opposite first and second longedges 22, 22′ and opposite first and second short edges 23, 23′, andfour corresponding corners or vertices 24, 24′, 25, 25′ between adjacentlong and short edges.

In addition to the suction plate 10, the lifter actuation system 4comprises six suction lifters 28, 28′, 28″ proximate three of the foursuction plate edges, specifically along the first long edge 22 and alongthe adjacent first and second short edges 23, 23′. These six suctionlifters are arranged in two groups 31, 31′ of three suction lifters inproximity with one another, a first one of these groups 31 having afirst suction lifter 28 proximate a first vertex 24 and the other ofthese groups 31′ having a first suction lifter 28 proximate a secondvertex 24′. The other two suction lifters of each group have a secondsuction lifter 28′ positioned proximate the first long edge 22, and athird suction lifter 28″ positioned proximate either the first or thesecond short edge 23, 23′, in each case equidistantly from thecorresponding vertex such that the three suction lifters 28, 28′, 28″ ineach group are located on the vertices of an equilateral triangle. Aswill be explained below, the benefit of this arrangement is that itfacilitates the initial plucking of one or two corners of a sheet to belifted prior to lifting of the entire sheet by the suction liftingsurface 11.

The lifter actuation system 4 further comprises along the second longedge 22″ an elongate bar 26 that is movably mounted along the secondlong edge 22′ of the suction plate 10 between third and fourth cornersor vertices of the suction plate. The elongate bar is omitted in FIG. 2,but is shown in more detail in FIGS. 25 and 26. The bar 26 comprises aseries of nozzles 27 connected to the source of negative air pressure 14(also called “vacuum pressure”) for providing a vacuum suction into thenozzles. The movable elongate bar will be described in greater detailbelow.

Reference is now made to FIGS. 2 to 5, which show various views of themain structural components of the vacuum lifter apparatus 4. An upperside 29′ of the substantially planar lower suction plate 10 is affixedto a lower side 34 of a chassis 30. The suction plate is thereforesupported beneath the upper chassis.

The chassis 30 has a centrally located mounting portion, comprising amounting bracket 100 to which a manipulating end of the robotic arm 7 isconnected. The chassis is also affixed substantially centrally withrespect to the centre of gravity of the suction plate 10 The vacuumlifter apparatus 4 is therefore substantially balanced about itsmidpoint.

An upper side 34′ of the chassis 30 has an air outlet 32 for connectionto the airflow suction system, for example by a flexible hose 33 asshown in FIG. 1, to the source of vacuum pressure 14. The air outlet 32conveys to the suction plate 10 vacuum pressure through a plurality ofvalve apertures 35 in an upper wall 115 of a chassis housing 50 along aplurality of air flow paths or channels 39 that extend through thechassis and suction plate to provide suction lifting pressure to theupper surface 9 of the articles 5 to be lifted. In this example, the airchannels 39 are provided between an upper wall 12′ of the vacuum plateand the upper wall 115 of the chassis housing 50.

The suction lifting surface comprises a plurality of laterally adjacentportions 36. In this example, as shown most clearly in FIG. 3, there areeight such portions. These portions are modular in form, i.e. beingadapted to be fitted together into a whole. Each suction plate liftingsurface portion 36 is provided by a metallic lower plate 37 of acorresponding suction plate module 40, 40′, 40″. The modules are squarein outline and arranged in a two by four array such that four modulesmake up each of the suction plate long sides 22, 22′ and two of themodules make up each of the suction plate short sides 23, 23′.

When joined together, the lower plates 37 provide the lower wall 12 ofthe suction plate 10. Each module has a metallic upper plate 37′, whichis parallel to, and spaced apart from the lower plate 37. When joinedtogether, the upper plates 37′ provide the upper wall 12′ of the suctionplate 10. The upper and lower plates each have a square outline, eachbeing bounded by four edges 38, 38′.

Each upper plate 37′ has around its edges 38′ four similar metallicmembers 45 each of which is a folded extension of the upper plate,extending downwards along a fold line 46′ in the metallic material froma corresponding edge 38′ to provide an inner side plate member for themodule.

There are three varieties of module 40, 40′, 40″, depending on theirlocation in the suction plate 10 and the way each module is affixed tothe chassis 30. Specifically, there are four similar suction platemodules 40 arranged in a two-by-two array in a main, central portion ofthe suction plate 10, and four suction plate modules of differenthandedness 40′, 40″ at the corners 24, 24′, 25, 25′ of the suction plate10.

The main differences between the modules, apart from lower and upperclearance apertures 47, 47′ for the two groups 31, 31′ of suctionlifters in, respectively, the lower and upper plates 37, 37′, are in theshape of four side plate members 41-44, 41′-44′, 41″-44″ each of whichextends upwards along a fold line 46 in the metallic material from acorresponding edge 38 to provide an outer side plate member for themodule. In addition, in each module, two or three of the side platemembers extend upwards above the upper plate 37′ to present tabs 48.Each tab 48 abuts similar tabs 48 from side plate member extensions ofan adjacent module and when joined together these tabs formcorresponding flanges 49 which slot into corresponding slots 49′provided on the lower side 34 of the chassis 30.

A particular advantage of the tabs 48 is that these are an example of anupwards extension of the lower plate of each one of the suction platemodules. Because these extensions are joined directly to the upperchassis, the weight borne by the suction plate is directly conveyed tothe chassis at least in part by material contiguous with the lowerplate. This is a very strong form of construction—the upper chassis andlower plate form an overall monocoque chassis. A monocoque chassis is astructure which integrates body (e.g. vacuum plate) and chassis (e.g.upper chassis) together to form a composite structure which has betterstiffness as well as weight advantage. In a monocoque chassis the stressgenerated during lifting or motion is distributed among the structureand does not form localised stress which would result in deformation.The structure allows for a lighter structure (in this example typicallyabout 80 kg to 90 kg) to have greater strength, which provides asignificant advantage in terms of robotic actuators, which becomeincreasingly expensive, or alternatively slow, when the weight to beborne at by the robot arm exceeds about 100 kg.

The slots 49′ are provided by parallel gaps between opposed pairs ofbrackets of which there are three types, 51, 51′, 51″, bonded to a lowersubstantially concave lower side 52 of the main housing or body 50 ofthe chassis. The brackets 51, 51′, 51″ together with engagement of theflanges in slots, form longitudinal and transverse walls which providetransverse air pressure isolation of one void or air chamber 56 aboveeach suction plate module from a corresponding void or air chamber 56 ofan adjacent suction plate module.

When the lower and upper plates 37, 37′ are brought together, the innerside plate members 45 make a close sliding fit inside the outer sideplate members 41-44, 41′-44′, 41″-44″. It is preferred if mating sideplate members, including abutting upwards extensions, are bondedtogether by adhesive to form the suction plate 10, although other means,for example rivets or clinch joins may be used instead of, or inaddition to, adhesive.

The suction plate, once formed, is then secured to the lower side 34 ofthe chassis 30 by slotting the flanges 49 into the slots 49′. It ispreferred if mating flanges and slots are bonded together by adhesive.Other securing means may be used, either additionally or alternatively,for example bolts or rivets pinning the assembled flanges and slots.

The concave lower side 52 of a main body 50 of the chassis is bounded bya continuous rim 53 which preferably is a lip that extends laterallyoutwards to a peripheral edge 54 of the chassis main body. The rimpresents a downwardly facing surface 55 to the upper wall 12′ of thesuction plate. The rim downwardly facing surface lies in a plane, sothat the rim can be secured to the suction plate upper wall, preferablyby bonding using an adhesive, which also provides a peripheral air sealfor the chambers 56. Other securing means for example rivets, mayalternatively or additionally be used. When the chassis main body 50 andsuction plate 10 are secured together in this way, the generally concavelower surface 52 of the lower side of the chassis main body 50 andopposite portions of the suction plate upper wall form the air chamber56 above a corresponding one of the suction plate modules.

It is, however, most preferable if there is an air-tight seal providedbetween the rim 53 and the suction plate upper wall 12′, and alsobetween opposite sides of the joined flanges and brackets, so that eachair chamber is isolated in terms of air pressure from adjacent airchambers and also the surrounding ambient air.

The chassis 30 is therefore separated at intervals from the suctionplate upper side or wall 12′ to provide the plurality of air chambers 56between the chassis and suction plate. Each air chamber is alsoconfigured to convey the vacuum pressure to a corresponding one of thesuction plate portions. In this example the upper plate of the suctionplate module has a plurality of apertures or holes 13′ therein, the airflow paths 39 extending from the holes 13 in the lower wall 12 of thesuction plate 10 and through the holes 13′ in the upper wall of thesuction plate and into each chamber 56 and to the corresponding valveaperture 35.

Each suction lifting surface module has the same number and pattern ofsuction holes 13, apart from two to which the two groups 31, 31′ ofsuction lifters are mounted, which are provided with correspondingclearance apertures 47, 47′ in the lower and upper module plates 37,37′. Each of the suction lifting surface portions comprises a differentsub-set of the orifices 13 through which, in use, air is drawn alongseparated airflow paths to provide suction lifting pressure to eachportion of the suction lifting surface.

Reference is now made to FIGS. 6 to 11. As mentioned above, the airflowsuction system comprises at least one air outlet 32 for connection tothe source of vacuum air pressure 14. In one aspect of the invention,between the, or each, outlet and the suction plate there is at least oneairflow manifold, this manifold comprising a plurality of branched ends,and these ends being configured to convey the vacuum air pressure fromthe, or each, outlet to corresponding portions 36 of the suction plate.In the example described above, the air chambers 56 provide part of thismanifold.

Another part of the manifold is provided by at least one valve manifold.In this example, there are two such valve manifolds 58, 58′, each onehaving an inlet side with four of the valve apertures 35, and each onehaving an outlet side leading to the air outlet 32, either directly, inthe case of a first valve manifold 58 or by a connecting pipe 59 in thecase of a second valve manifold 58′.

The inlet side of each valve manifold is provided by corresponding firstand second valve plates 60, 60′. The outlet side of each manifold isprovided by corresponding first and second valve manifold covers 61,61′.

Associated with each valve aperture 35 is a valve actuator 62, which inthis example is pneumatic, although other type of valve motor could beused, for example electric or stepper motor actuators. The pneumaticsupply to the valve actuator is via one of a set of electronicallycontrolled control valves 70 located on the upper side 34′ of thechassis 30. The control valves are controlled by the controller 8. Forclarity, individual wires to the control valves 70 and individualpneumatic pipes are not illustrated, however such conventionalconnections will be apparent to those skilled in the art.

The valve actuator 62 drives a valve slider 63 which is movable to openand close the valve aperture 35. Each valve slider is mounted on anupstream face 64 of one of the valve plates, that is, the side of theplate facing into one of the corresponding air chambers 56. Each valveactuator is mounted on a downstream face 64′ of one of the valve plates,that is, the side facing into the valve manifold.

As shown in FIGS. 12 and 14, the flanges, which are held together by alayer of cured adhesive 65, cross at four cruciform junctions 66, two ofwhich are centered directly beneath corresponding valve plates 60, 60′with one of the four valve apertures being located in one of the fourquadrants around the junction. This is so that each valve controls theair flow from just one of the air chambers 56 and so that each of thevalve plates 60, 60′ spans a cruciform junction 66′ of slots betweenbrackets 51, 51′ 52″. An air seal is made around a peripheral region 67of the upstream face of each valve plate and the main body 50 of thechassis to which the valve plate is bolted, by means of a gasket 68, asshown in FIG. 11. The gasket also makes an air seal with the brackets51, 51′, 51″ where these cross beneath the valve plate.

As shown in FIG. 7, the valve actuators are linear actuators each ofwhich drives a piston 69. The piston is connected to a bracket 71affixed to the valve slider, this bracket extending upwards through thevalve aperture 35. The valve plate has opposite lateral sides each ofwhich slides inside a groove 72 provided by a pair of mirror-image siderails, one of which 73 is shown in FIG. 10.

Reference is now made to FIGS. 12 to 16, which show further details ofthe suction plate modules 40, 40′, 40″. The upper, lower and side platesof each module provide a substantially hollow housing 80. Asubstantially hollow interior 74 of each housing is spanned by ahoneycomb reinforcing structure 75 which comprises contiguous hexagonalcells 76 having vertically extending cell walls 77 each of which isperforated by at least one aperture or hole 78 to allow cross-flow ofair within the reinforcing structure towards cells which are within thefootprint of one or another of the array of holes 13′ in upper wall 12′of the suction plate 10. The bottom and top portions 79, 79′ of eachcell wall, or at least a substantially complete proportion of cellswalls, are bonded by means of adhesive. The adhesive will, in general,be a liquid adhesive before curing to set the adhesive 81, shownschematically in FIG. 16 as zig-zag lines and in more detail in thesection of FIG. 20, to corresponding lower and upper inner surfaces 82,82′ of the housing 80. It is preferred if substantially all of the cellwall bottom and top portions are bonded to the corresponding housinginner surfaces. The reinforcing structure is sandwiched between a lowertray, which is provided by the lower plate 37, and an upper lid, whichis provided by the upper plate 37′.

Preferably, before bonding of the laterally air-permeable honeycombreinforcing structure 75 inside the housing interior 74, the cells aresecured within an outer frame or band 83 which may extend continuouslyaround the periphery of the cells. L-shaped corner reinforcement tabs 84may also be provided, which are preferably bonded to internal cornerswithin the housing interior, to provide additional strength and seal anygaps between the folded side plate members.

The reinforcing hexagonal cell structure is made from parallel metallicstrips, bonded together along transverse lines and then punched throughor drilled to form apertures for the cell walls. The strips are thenpulled apart to form the cellular structure as shown in FIG. 16. Whenbonded inside the housing interior 74, this provides reinforcementagainst bending or twisting in the vertical direction, while addinglittle extra weight to the suction plate module. By keeping the weightdown in this way, while maintaining sufficient rigidity, the size of therobotic arm and actuation system can be reduced while helping toincrease the permissible acceleration in use.

Preferably, the rectangular array of suction holes 13 is made to fitregularly within the repeating honeycomb pattern of the reinforcingstructure 75, in order to avoid a situation where some of the holes arebeneath the cell walls or so close that the adhesive blocks some suctionholes 13. This can be done by orienting one axis of the array of holesparallel with two opposite sides of the cell walls and the other axistherefore being perpendicular to these opposite cell walls. It can beshown that if “x” is the hexagonal cell wall length, then the array ofholes 13 will fit regularly inside the hexagonal array of cell walls ifthe spacing of holes in the parallel direction is 3·x/2 and the spacingof holes in the perpendicular direction is x·(√3)/2.

Reference is now made to FIGS. 17 and 18, which show an alternativereinforcing structure 175, which is in the form of a grid, which may berectangular, but is preferably square. The grid reinforcing structure ismade from two orthogonal sets of elongate parallel metallic strips 170,preferably aluminium sheet 1 mm thick, that provide square cells 176.The sets of strips intersect to provide four walls 177 for each cell176.

The individual strips of both sets are the same. The strips 170 have alength that spans the width or length of the hollow interior 74 of themodule housing 80. Each strip has along its length spaced slots 171 thatextend transversely across the width of each strip from one long edge,the length of each of the slots being just over half the width of thestrip. The width of each slot is such each slot holds another stripextending at right angles, and the spacing of the slots is such that theslots of intersecting strips interleave with each other with the longedges aligned in parallel planes at lower and upper ends 179, 179′ ofthe square cell walls. In FIG. 9, one of the walls 177 is omitted sothat the slots 171 for receiving one strip can be seen fully.

The slots 171 are each formed by cutting a stack (not shown) of parallelstrips with a saw. The strips are then placed in two jigs (not shown),each jig holding the strips in the correct parallel orientation andspacing. The jigs are then brought together to interengage all the slotsat the same time. Optionally, the interengaging slots may be bondedtogether with adhesive to increase the strength of the reinforcingstructure. When bonded inside the hollow interior 74 of the housing 80,this reinforcing structure provides reinforcement against bending ortwisting in the vertical direction, while adding little extra weight tothe vacuum plate module 40, 40′, 40″.

Another advantage of this arrangement is that the slot spacing can beequal to the reinforcing wall height, as illustrated, so that a singleround hole 178 can be formed in the wall midway between each slot. Theseholes 178 are formed by drilling through the strips when these are heldparallel together in a stack of strips.

A further advantage of this arrangement is that the grid can be alignedwith the axes of the array of holes, and the hole spacing can be thesame along both axes while still avoiding overlap of the suction holes13.

Further reinforcement and weight reduction is provided by the way inwhich the arch-like portions of the chassis (i.e. those lobe-like,branched end parts providing each air chamber between suction plate andchassis) span each suction plate module, whilst providing a manifold forthe suction plate having branched ends or lobes 120, one for eachsuction plate module. The transversely extending side walls of each lobe120 provide lateral reinforcement across the width of the suction plate.

The chassis main body 50 is preferably moulded in a fibre-reinforcedcomposite material, most preferably a carbon fibre composite. Localisedstresses around eight internal corners 121 of the main chassis lobes 120are relieved by eight L-shaped aluminium brackets 122 that are bolted tothe lower side 34 of the chassis interior around the interior corners.

In addition, it is preferred if the brackets 51, 51′, 51″ are alsomoulded in a fibre-reinforced composite material, most preferably acarbon fibre composite. The suction panel modules are formedpredominantly from sheet metal, for example aluminium or stainlesssteel. When assembled together, the suction panel and chassis providetruss-like reinforcement across the lateral extent of the assembledstructure.

Reference is now made to FIGS. 19, 21 and 22, which show in more detailthe suction lifters 28, all of which are the same, apart from theirlocations on the suction plate 10. Each suction lifter comprises adownwardly oriented suction cup, 87 the cup being movably mounted in asubstantially vertical direction relative to the suction plate 10. Eachsuction lifter is provided with a vacuum pressure from a source of airpressure, which may be both negative and positive air pressure 14, 14′.More generally, the suction cup is connected to a source of air pressurefor providing air suction to the cup for plucking upwards a local areaof the article to be lifted. In this example, the source of air pressureis the negative source of air pressure 14, however it is alternativelypossible to generate a negative pressure at a suction cup using apositive source of pressure directed across a venturi pipe.

Each suction lifter also has two connections 85, 86 for air lines. Oneconnection 85 is connected to a conduit 85′ which runs, via one of thecontrol valves 70 to the source of negative air pressure 14 forproviding suction pressure to the downwardly directed compliant suctioncup 87. The other connection 86 is connected to a conduit 86′ whichruns, via one of the control valves 70 to the source of positive airpressure 14′ for providing a driving pressure to expand a bellowsactuator 88 which pulls upwards a piston 89 on which the suction cup 87is mounted. The piston is downwardly biased by a coil spring 91surrounding the piston and which acts between an annular flange 92proximate the suction cup 87 and an annular seat 93 around a sleeve 94inside of which the piston 87 is slideably mounted.

A cylindrical outer sleeve 95 extends downwards away from the annularseat 93 and around a proximal portion of the piston when extended. Thelength of the outer sleeve is essentially the same as the thickness ofthe suction plate, between the lower and upper sides 29, 29′, and thediameter is a close sliding fit inside the lower and upper clearanceapertures 47, 47′ for the suction lifters. Preferably, the lowerclearance aperture 47 is of slightly smaller diameter than the upperclearance aperture, in which case a distal end 90 of the outer sleeve 95is provided with an annular step 96 having a reduced diameter, asillustrated in FIGS. 21 and 22, so that the step in the outer sleeve canbe used to make a secure join around the aperture in the lower side ofthe suction plate, for example with a bead of adhesive (notillustrated).

In normal operation, the positive pressure is applied to retract thepiston until the suction cup 87 is recessed fully within the outersleeve 95. In this orientation, the suction lifter does not affect thehandling of the material by the suction plate 10. As shown in FIG. 19,when a sheet is to be lifted, the suction plate 10 is lowered intoproximity with the sheet with no positive pressure applied to thebellows so that the suction lifters 28, 28′, 28″ are in the droppedorientation. Suction is then applied to the suction cup to pull alocalised area 108 of the sheet material upwards, and optionally thesuction plate may also be lifted to further disengage the top sheet fromthe one below. This admits air in the localised area between the top andbottom sheets, thereby helping to reduce problems in separating thelayers owing to vacuum stiction from ambient air pressure, or mechanicalor electrostatic stiction between very smooth surfaces. As a result, itis easier to subsequently peel upwards the top sheet, by then applyingvacuum through the array of holes 13 in the lower wall 12 of the suctionplate.

Optionally, a jet of air 57 may be laterally applied where the sheet islocally lifted in order to further separate the layers.

Preferably, the suction lifters are retracted while maintaining vacuumsuction to the suction cups, thereby pulling the localised area 108 ofthe sheet directly up against the underside 29 of the suction plate 10.

Most preferably, the plurality of control valves 70 for the suctionplate modules are activated sequentially, with those nearest thelocalised area 108 being activated first and those furthest away beingactivated last. This helps provide maximum vacuum to the first suctionplate modules to be activated and also pulls the remainder of the sheetto the underside 29 of the suction plate 10 in a progressive manner,which can help to avoid wrinkles in very thin sheet material.

The localised area 108 is preferably either a strip along one edge ofthe sheet material article or a corner portion. This is so that thesubsequent progressive lifting is directed away from the localised areatowards other portions of the sheet not yet peeled up from the stack ofarticles, or from the work surface. A particular advantage of this isthat the sheet material article becomes progressively adhered to thevacuum lifting surface, which can help to flatten out any wrinkles orother types of unevenness in the lifted sheet material article 5. Thisovercomes a problem with cardboard, which often becomes distorted from aplanar orientation, particularly when the relative humidity of the airis elevated. In the prior art, when a vacuum lifter makes contact at thesame time across the full extent of a sheet to be lifted, suchunevenness can result in creases or other types of non-planar formsbeing exaggerated or impressed into the lifted sheet material.

The progressive lifting of the sheet material article 5 is shown in FIG.20. Once the localised portion 108 is adhered, the suction from adjacentsuction holes 13 pulls adjacent areas upwards first, and the sheetmaterial is then peeled upwards in directions extending away from theinitial localised area 108.

The suction holes 13 in the lower wall of the suction plate arepreferably punched holes, not drilled holes, produced by a punch anddie. As shown in FIG. 20, each hole 13 presents on the lower surface 11of the suction plate 10 an outwards funnel surface 125 at the entranceto a main bore 126 of the hole in the metal sheet, having acorresponding convex curve that expands radially outwardly from themain, substantially cylindrical part of the bore of the hole, so thatthe surface of the punched hole 13 expands outwards progressively with abell shape, for example like a trumpet bell. The funnel surfacetherefore provides a downwardly flared entrance 128 to airflow 130 intothe bore 89 of the hole 13. Opposite this entrance 128, the bore has anexit 129 for the air pulled through the hole, this exit being surroundedby a rim 135 that extends above the surrounding inner surface 82 of thelower wall 12 of the vacuum plate 10. A particular advantage of the rims135 is that these help to prevent flow of adhesive 81 into the holesprior to curing of the adhesive.

The increased suction area afforded by the bell shaped entrances 128 tothe suction holes 13 increases the suction force for the providedsuction air pressure. The smooth internal surfaces of the holes whenproduced by punching, as opposed to drilling, increases the air flowvelocity and results in more efficient generation of suction liftingpressure.

The adhesive 81 bonding the honeycomb or grid structure to the internallower and upper walls 12, 12′ of the module housing will, in general, beapplied as a liquid adhesive before curing to set the adhesive, as shownin FIG. 20. This can be done by dipping one end of the cell walls in anadhesive. The adhesive will lap most or all of the abutment between thecell walls and adjacent 82, 82′ of the lower and upper walls 12, 12′.

FIGS. 1, 19, 23 and 24 also show how the suction plate has one or moredownwardly oriented video cameras 97 mounted to a track or rail 98 thatis provided on at least one edge 22 of the suction plate. The mountingrail allows the video camera to be slid along the length of the edge toa desired position. Electrical connections 99 run from the video camerato the controller 8 so that the camera can be used a part of a machinevision system to permit more accurate positioning of the suction plateduring lifting and deposition of sheet material.

FIGS. 25 and 26 show the elongate movable bar 26 in more detail. The barhas opposite ends 101 from each of which a pivot arm 102 extends in adirection transverse to the length of the bar. The arm has at a distalend 103 a pivot joint 104, by which the arm and bar are pivotablyconnected to a mounting bracket 105, that is also secured to a mountingtrack or rail 98′ similar to the one mentioned above.

A pair of linear actuators 106, 106′, in this case pneumatic actuators,is provided, one at each end 101, 101′ of the bar 26, which actdownwards on the suction plate upper side 29′ to move the bar up anddown. The linear actuators are controlled via corresponding ones of thecontrol valves 70. When up, a lower surface 107 of the bar is at orslightly above the level of the underside 29 of the suction plate 10.When down, the lower surface is beneath the level of the underside ofthe suction plate.

The lower side 107 of the bar is perforated along its length by nozzles27 for providing a suction airflow 109 along the length of the bar. Thebar has a hollow interior (not illustrated), which acts as a plenumchamber of the nozzles. An upper side 107′ of the bar 26 is providedwith at least one air outlet connection 110 for connection to thenegative source of air pressure 14. Prior to lifting a sheet, ordepositing a sheet on the work station surface 15, the bar may be usedto vacuum debris off the corresponding upper surface. FIG. 26 shows thevacuuming of the work surface; the same principles apply when vacuumingthe top of a sheet material article. The controller 8 controls thepositioning of the suction plate 10 to bring this into proximity withthe surface, at one side of an area to be vacuumed. The controller thenactivates the linear actuators 106, 106′ to lower the bar, which dropsunder its own weight into position for vacuuming. The controller thenactivates the source of negative air pressure and moves the suctionplate in a direction transverse, and preferably perpendicularly, to thelength of the bar, either in the direction 111 shown in FIG. 26 or theopposite direction. Any dust or debris 112 on the surface will then bevacuumed by the suction airflow 109.

After the vacuuming operation is completed, the controller shuts off theflow of air from the source of negative air pressure 14 and activatesthe linear actuators 106, 106′ to raise the bar 26 into the raisedposition, as shown in FIG. 25.

As will be appreciated from the above discussion, there are numerouselectrical wires, or conduits for air flow or pneumatic lines to be madeto devices around the periphery of the suction plate. Some devices, suchas cameras, may also employ fibre optic connections. It is important toprotect such cables, air lines or conduits. Therefore, the upper side34′ of the chassis main body 50 is preferably provided with number ofchannels or grooves 113 therein, generally radiating outwards from theregion of the mounting bracket 100. For clarity, not all such wires,cables or conduits are shown in all drawings, however, at least some ofthese are preferably routed within the grooves, and preferably coveredover at points with adhesive tape or cable tie-downs (not shown), toprovide protection and help prevent such components from moving relativeto the chassis, and possibly causing wear or stress, for example atconnections.

The invention, in its various aspects, as defined by the accompanyingclaims, therefore provides a versatile, and relatively strong andlightweight vacuum lifter apparatus which may be employed in differentmodes of operation as part of an automated sheet material processingapparatus in which sheet material articles are to be lifted anddeposited at various locations or work stations.

Listing Of Reference Numerals

1 sheet material processing apparatus

2 sheet material cutting work station

3 vacuum plate lifting system

4 vacuum lifter apparatus

5 sheet material articles

5′ processed sheet material articles

6 sheet material lifter actuation system

7 five-axis robotic arm

8 control system

9 upper surface of sheet material articles

10 suction plate

11 suction lifting surface of suction plate

12 lower wall of suction plate

12′ upper wall of suction plate

13 array of holes in lower wall of suction plate

13′ array of holes in upper wall of suction plate

14 source of negative and positive air pressure

15 cutting surface

16 table top or plate

17 holes in table top or plate

18 input stack of sheet material articles

18′ output stack of processed sheet material articles

19 cut lines in processed sheet material article

19′ fold lines in processed sheet material article

20 movable blade of cutting work station

21 useful material of processed sheet material article

21′ waste material of processed sheet material article

22 first long edge of suction plate

22′ second long edge of suction plate

23 first short edge of suction plate

23′ second short edge of suction plate

24 first corner or vertex of suction plate

24′ second corner or vertex of suction plate

25 third corner or vertex of suction plate

25′ fourth corner or vertex of suction plate

26 elongate movable bar

27 nozzles along length of bar

28 suction lifters proximate first and second vertexes

28 first suction lifter

28′ second suction lifter

28″ third suction lifter

29 lower side of the suction plate

29′ upper side of the suction plate

30 upper chassis

31 first group of three suction lifters

31′ second group of three suction lifters

32 air outlet on chassis

33 flexible hose of airflow suction system

34 lower side of the chassis

34′ upper side of the chassis

35 valve apertures

36 suction plate portions

37 lower plate of suction plate module

37′ upper plate of suction plate module

38 edges of lower plate

38′ edges of upper plate

39 air flow paths to valve apertures

40 suction plate module (first type)

40′ suction plate module (second type)

40″ suction plate module (third type)

41-44 outer side plate members of lower plate (first type)

41′-44′ outer side plate members of lower plate (second type)

41″-44″ outer side plate members of lower plate (third type)

45 inner side plate members of upper plate

46 fold line in lower plate

46′ fold line in upper plate

47 clearance apertures for suction lifters in lower plate

47′ clearance apertures for suction lifters in upper plate

48 tabs formed by upwards protections of outer side plate members

49 flanges provided by extensions of outer side plate members

49′ slots provided by opposed brackets

50 main body of chassis

51 brackets affixed to underside of main body of chassis (first type)

51′ brackets affixed to underside of main body of chassis (second type)

51″ brackets affixed to underside of main body of chassis (third type)

52 concave lower side of main body of chassis

53 rim of chassis main body

54 peripheral edge of rim of main body

55 downwardly facing surface of rim of main body

56 air chambers between suction plate and chassis

57 jet of air

58 first valve manifold

58′ second valve manifold

59 connecting pipe between first and second valve manifolds

60 first valve plate

60′ second valve plate

61 first valve manifold cover

61′ second valve manifold cover

62 valve actuators

63 valve sliders

64 upstream faces of the valve plates

64′ downstream faces of the valve plates

65 layer of cured adhesive holding flanges together

66 cruciform junction of flanges

66′ cruciform junction of slots between brackets

67 peripheral region of the upstream face of valve plate

68 gasket for valve plate

69 valve actuator piston

70 control valves

71 valve plate bracket

72 grooves in which valve slide plate lateral edges slide

73 slide rails providing grooves

74 substantially hollow interior of housing

75 honeycomb reinforcing structure

76 hexagonal cells of honeycomb reinforcing structure

77 vertically extending walls of hexagonal cells

78 lateral aperture or holes in hexagonal cell walls

79 bottom portions of hexagonal cell walls

79′ top portions of hexagonal cell walls

80 suction plate module housing

81 adhesive for bonding cell walls to housing inner surfaces

82 housing lower inner surface

82′ housing upper inner surface

83 outer frame for honeycomb reinforcing structure

84 corner reinforcement tabs

85 connections on suction lifter for negative pressure

85′ connection conduit for negative pressure

86 connections on suction lifter for positive pressure

86′ connection conduit for positive pressure

87 suction cup

88 bellows actuator

89 piston of suction lifter

90 distal end of outer sleeve

91 coil spring

92 annular flange proximate suction cup

93 annular seat for coil spring

94 piston sleeve

95 outer sleeve around spring and piston

96 annular step in distal end of outer sleeve

97 video cameras

98 mounting rail

99 electrical connections to video camera

100 mounting bracket of chassis

101, 101′ opposite ends of bar

102 pivot arm

103 distal end of pivot arm

104 pivot joint

105 mounting bracket for pivot joint

106, 106′ linear actuators for bar

107 lower side of bar

107′ upper side of bar

108 localised area of sheet

109 suction airflow of air from nozzles

110 air outlet connection for bar

111 bar sweeping direction

112 vacuumed dust or debris

113 grooves in upper side of chassis main body

115 upper wall of chassis

120 lobes of chassis manifold

121 internal corners of lobes

122 L-shaped brackets in internal corners of chassis interior

125 outwards funnel surface holes in lower wall of suction plate

126 main bore of holes in lower wall of suction plate

128 downwardly flared entrance main bore of holes of suction plate

129 exit for the air pulled through the holes in lower wall of suctionplate

135 rim surrounding the air exit of holes of suction plate.

170 strips of metal used to form square grid reinforcement

171 slots in strips

175 grid reinforcing structure

176 square cells of grid reinforcing structure

177 vertically extending interlaced linear walls

178 lateral aperture or holes in square cell walls

179 second (upper) ends of square cell walls

179′ first (lower) ends of square cell walls

181 adhesive for bonding cell walls to module housing inner surfaces

1. A vacuum lifter apparatus for lifting sheet material articles,comprising an upper chassis, a modular lower suction plate supportedbeneath the chassis, a controller and a source of vacuum air pressure,the suction plate comprising a suction lifting surface for providingvacuum lifting pressure to said articles, wherein: the modular suctionplate has a plurality of side-by-side modules, each module providing adifferent portion of the suction lifting surface and having one or moreair outlets, said outlets of one module being separate from said outletsof other modules and being in fluid communication with the correspondingportion of the suction lifting surface and not with different portionsof the suction lifting surface; the chassis comprises at least one airoutlet connected to said source of vacuum air pressure for conveyingsaid vacuum pressure to the suction lifting surface of the suctionplate, and a plurality of separate air flow channels through thechassis, each of said channels leading from said outlets of one of saidmodules to said outlet of the chassis; and said apparatus furthercomprises for each air flow channel an associated air flow valve and avalve actuator, the controller being operatively connected said valves,and the controller being configured, in use, to open and close saidvalves to separately control the vacuum pressure transmitted along saidchannels to each one of said modules whereby the vacuum pressureconveyed to each one of said different portions of the suction liftingsurface is individually controllable by the controller.
 2. The vacuumlifter apparatus of claim 1, in which said portions of the suctionlifting surface are arranged in an array, the controller is configuredto sequence opening of said valves to convey said vacuum pressure tosaid portions at different times such that vacuum pressure appears at afirst one of said portions first and a second one of said portions last,said first and second portions being on opposite sides of said array. 3.The vacuum lifter apparatus of claim 2, in which there is at least oneintervening portion of the suction lifting surface between said firstand second portions, and the controller is configured to sequence theopening of said valves to convey said vacuum pressure to saidintervening portions sequentially in time such that said conveyedpressure appears as a wave spreading across the suction lifting surfacestarting at said first portion and ending at said second portion.
 4. Thevacuum lifter apparatus of claim 1, in which the chassis is separated atintervals from the suction plate upper side to provide a plurality ofair chambers between the chassis and suction plate, each air flowchannel extending through one of said chambers.
 5. The vacuum lifterapparatus as of claim 1, in which each suction module comprises ahousing, the housing comprising opposite top and bottom walls, saidbottom walls together providing a lower side of the suction plate andsaid top walls each providing said outlets of said modules.
 6. Thevacuum lifter apparatus of claim 5, in which said bottom walls are eachperforated to provide orifices through which, in use, air is drawn alongair flow paths through said top wall outlets and into said channelstowards said air outlet of the chassis to provide said suction liftingpressure.
 7. The vacuum lifter apparatus of claim 2, in which thechassis is separated at intervals from the suction plate upper side toprovide a plurality of air chambers between the chassis and suctionplate, each air flow channel extending through one of said chambers. 8.The vacuum lifter apparatus of claim 3, in which the chassis isseparated at intervals from the suction plate upper side to provide aplurality of air chambers between the chassis and suction plate, eachair flow channel extending through one of said chambers.